Air compressors with oil content below what percentage can be called oil-free
An air compressor with an oil content of less than 0.01 mg per cubic meter can be called an oil-free air compressor. In other words, this value is 0.01ppm, that is, 0.01 parts per million, which can be said to be almost negligible.
For example, if you spread a drop of oil evenly into a very large room, the oil content in the room is probably close to this figure. Therefore, when the gas discharged from an air compressor is less than this level of oil, the industry recognizes that it is oil-free.
For ordinary oil-injected screw air compressors, the exhaust oil content is generally about 3 mg per cubic meter, which is hundreds of times higher than the 0.01 standard, so it can only be regarded as an oil machine.
What about the water-lubricated air compressor? It uses water instead of oil to seal the rotor and take away the heat. Because the entire compression process does not use oil at all, the discharged gas naturally does not contain oil, and the oil content can easily be less than 0.01 mg per cubic meter, or even lower. In other words, the water-lubricated air compressor is naturally suitable for reaching the oil-free standard in principle. It does not need to be pulled hard by adding a filter at the back, but there is no oil from the source. This is why food, medicine, electronics, which are particularly sensitive to air, are increasingly choosing water-lubricated air compressors.
